1. Technical Field
The present invention relates to a structure that may be adopted in heat exchange tubes in a heat exchanger having a tank formed through extrusion molding and tubes formed through roll forming, which are bonded through a brazing process in a furnace.
2. Background Art
Today, heat exchange tubes in a heat exchanger having tanks and heat exchange tubes formed independently of each other are often manufactured through roll forming by bending a thin rolled sheet material so as to reduce the number of dies used in the manufacturing process for cost reduction. In the roll forming process, a sheet member needs to be bonded with a high level of airtightness at the bonding regions. This requirement is addressed in a method (see, for instance, Japanese Unexamined Patent Publication No. H11-216592) in which a brazing material layer is formed so as to cover a surface of the sheet member on one side and the sheet member is brazed at the bonding regions by using the brazing material layer.
However, if the heat exchange tubes themselves are coated with a brazing material layer, as in the Japanese Unexamined Patent Publication mentioned above, problems such as the dispersion of the brazing material during the brazing process and erosion make it difficult to reduce the wall thickness of the material, and thus, the heat exchanger cannot be provided as a compact, lightweight and inexpensive unit.
Accordingly, an object of the present invention is to provide a heat exchanger achieving a smaller wall thickness for the heat exchange tubes and a reduction in the manufacturing costs by supplying brazing material from the tank side to be used to braise the heat exchange tubes at their bonding regions without covering the heat exchange tubes themselves with a brazing material layer.